Visual tracking assessment in a soccer-specific virtual environment: A web-based study

The ability to track teammates and opponents is an essential quality to achieve a high level of performance in soccer. The visual tracking ability is usually assessed in the laboratory with non-sport specific scenarios, leading in two major concerns. First, the methods used probably only partially reflects the actual ability to track players on the field. Second, it is unclear whether the situational features manipulated to stimulate visual tracking ability match those that make it difficult to track real players. In this study, participants had to track multiple players on a virtual soccer field. The virtual players moved according to either real or pseudo-random trajectories. The experiment was conducted online using a web application. Regarding the first concern, the visual tracking performance of players in soccer, other team sports, and non-team sports was compared to see if differences between groups varied with the use of soccer-specific or pseudo-random movements. Contrary to our assumption, the ANOVA did not reveal a greater tracking performance difference between soccer players and the two other groups when facing stimuli featuring movements from actual soccer games compared to stimuli featuring pseudo-random ones. Directing virtual players with real-world trajectories did not appear to be sufficient to allow soccer players to use soccer-specific knowledge in their visual tracking activity. Regarding the second concern, an original exploratory analysis based on Hierarchical Clustering on Principal Components was conducted to compare the situational features associated with hard-to-track virtual players in soccer-specific or pseudo-random movements. It revealed differences in the situational feature sets associated with hard-to-track players based on movement type. Essentially with soccer-specific movements, how the virtual players were distributed in space appeared to have a significant influence on visual tracking performance. These results highlight the need to consider real-world scenarios to understand what makes tracking multiple players difficult.


I kindly ask you to also specify and describe, in the "Supporting information"
section of the manuscript, what data are contained in supplementary files S3, S4, and S5.
Thank you for the reminder. Here are the added descriptions: -"S1 File. The mean ratio of successful visual tracking by participants in both experimental conditions." -"S2 File. The raw dataset (before the data is centered-reduced) used for the clustering of target-players in STRU condition. Each row represents an individual target-player and each column represents a situational feature (columns 2-9) or a visual tracking ratio (columns 10-12)." -"S3 File. The raw dataset (before the data is centered-reduced) used for the clustering of target-players in UNSTRU condition." The supporting files were rearranged in ascending numerical order according to their first appearance in the manuscript: -S1 File was first cited on line 293.
-S2 File and S3 File were first cited on line 326.
-S4 File and S5 File were first cited on line 352.

Reviewer 2 Point 3a:
In your response to this reviewer comment, you present a table showing tracking performance as function of soccer viewing frequency. You state that even though "mean visual tracking performance appeared to increase with the frequency of soccer game viewing, but we assumed that this effect was not significant due to the large standard deviation". I have plotted the data you presented, and computed 95% confidence intervals from your reported standard deviations and sample sizes. From these, it looks like there could be a significant effect, as in a few instances the means and confidence intervals of tracking performance across soccer viewing frequency do not overlap. Whichever the case, I suggest it is always best to verify ones' assumptions when possible. I thus ask you to explicitly test whether a statistical statistically significant effect exists in these data. Further, I believe the reviewer's main question was whether the observed differences between study groups could be explained by soccer viewing frequency. Thus it would be useful to test and report whether the three study groups differed significantly in soccer viewing frequency (e.g. by running a one-way ANOVA on viewing frequency, with sport practice as the between-subjects main effect. If the groups differ in viewing frequency the same way they differ in tracking performance, then this potential confound should be included and discussed in the discussion section of the manuscript. Moreover, when a reviewer brings up a question, it is good practice to address it both in the response letter as well as in the main manuscript, since future readers may have the same question. I thus ask you to incorporate your response to this reviewer comment in the main manuscript. This could be simply a few lines in the methods or the discussion section of the manuscript, where you point out the issue and report the result of your control analyses (once you have performed them).
Thank you for the insightful comment.
This control analysis has been added in the discussion of the manuscript ( 3. Reviewer 2 point 3b: As above, I ask you to report the result of these control analyses in the main manuscript. Thank you for the comment. As requested, the analysis has been added in the manuscript (lines 463-476): "Attentional demands in the field differ depending on the playing position. Differences in visual tracking performance have been observed between frontcourt and backcourt basketball players [16], and between frontward and backwards rugby players [19]. The defender's viewpoint was chosen in this study because most teammates and opponents can be seen within a maximum visual angle of 180°, which increased the crowding of the field of view by the players. With a more advanced viewpoint on the field, the players to be monitored would have been distributed 360°around the observer. A similar defender viewpoint was used in the study by Roca and colleagues (2013)  Thank you for the comment and the references to methods we were not aware of.